Foreign Currency and Local Currency

Folks,

Can anyone here please let me know under what circumstances do we use the below mentioned FMs.To my knowledge both these FMs does currency to currency conversion and the words FOREIGN and LOCAL are just nomenclature as far as the FMs are concerned.From the Code perspective I see only the following differences.

CONVERT_TO_FOREIGN_CURRENCY
CONVERT_TO_LOCAL_CURRENCY

CONVERT_TO_FOREIGN_CURRENCY

CATCH SYSTEM-EXCEPTIONS arithmetic_errors = 1.    IF tratex LT 0.      refe = - local_amount * tratex * tcurr-ffact * ref2           / ( 100000000000 * ref1 * tcurr-tfact ).    ELSE.      refe = local_amount * 100000000000 * tcurr-ffact * ref2           / ( tratex * ref1 * tcurr-tfact ).    ENDIF.
ENDCATCH.

CONVERT_TO_LOCAL_CURRENCY

CATCH SYSTEM-EXCEPTIONS arithmetic_errors = 1.    IF tratex LT 0.      refe = - foreign_amount * 100000000000 * tcurr-tfact * ref1           / ( tratex * ref2 * tcurr-ffact ).    ELSE.      refe = foreign_amount * tcurr-tfact * tratex * ref1           / ( 100000000000 * ref2 * tcurr-ffact ).    ENDIF.
ENDCATCH.

Thanks,
K.Kiran.